Time was invented because mankind did not know where the sun went and there was a fascination with it coming back. Later time was used to get you to work when your shift started. People think they can time travel but the past you know is not the same past that everyone else knows. Every single person has different ideas of the past and books about it were only someone's idea. We also think of the future but we are not there yet. We all live in the eternal now but we do time travel as we move forward using our earthly time machine.